A magnetic recording head employing a certain energy assist has been proposed to increase storage density of a hard disk drive. In addition to a conventional heat assist technique, a high-frequency (micro wave) assist technique with spin transfer torque (STT) has been proposed as such an energy assist, for example.
As to the high-frequency assist technique, the effect thereof becomes higher when the oscillation strength of an oscillator is stronger. However, when a temperature rises up around a working temperature of a hard disk drive, the high-frequency oscillation decreases and eventually, vanishes. Thus, cooling down the oscillator is required to deal with this problem.
Here, turning to a cooling technique of, for example, a current perpendicular element, the Peltier effect is used. By the Peltier effect applied to the current perpendicular element, there have been reports that the Au/Co junction may be used as a part of the current perpendicular element and that the Au/Ni—Cu junction may be used to obtain a voltage change corresponding to such a remarkable cooling effect of Δ200° C. Furthermore, a reproducing head using such cooling effects has been proposed.
The Peltier effect is a phenomenon in which heat absorption or heat radiation occurs when electric current is supplied to a junction surface between different materials. When the Peltier effect is applied, a potential difference occurs at the junction surface between the different materials, and the heat absorption is achieved when the electronic potential is up and the heat radiation is achieved when the electronic potential is down. The Peltier effect was discovered by Jean-Charles Peltier in 1834, and its cooling effect is represented by the following equation.ΔQ=ΠIΔt 
Here, ΔQ is an amount of heat radiated from or absorbed at the junction, Π is the Peltier coefficient inherent to the materials, Δt is a time of supplying the current, and I is the current. The efficiency of cooling or heating is determined based on the Peltier coefficient inherent to the materials, and thus, a suitable combination of the materials must be selected for the efficient cooling.
However, there is a technical difficulty in applying such a cooling method for the current perpendicular element directly to a cooling method for the high-frequency assist head. That is, the current perpendicular element or a reproducing head has such a simple structure that only electrodes are arranged therein other than the main part, i.e. the element, and thus, the heat may be absorbed at the element and correspondingly, the heat may be radiated from the electrodes distant from the element. On the other hand, the high-frequency oscillator of the high-frequency assist head is in such a complicated structure that the oscillator is interposed between a main magnetic pole and an auxiliary magnetic pole both of which are on a current path of the high-frequency assist head. Furthermore, the main magnetic pole and auxiliary magnetic pole are restricted to a FeCo alloy which exerts high saturation magnetization. Under these circumstances, the efficient cooling of the high-frequency oscillator has been a difficult issue in this technical field.